Kievan Rus

The Kievan Rus were a loose federation of East Slavic tribes, first ruled by Oleg of Novgorod in 882, and it fell apart by 1080 due to chaos in the court in Kiev. They were conquered by the Duchy of Novgorod in the 1000s and 1100s.

Background
The Rus were founded by the Drevliane, Severiane, and Vyatichi tribes, who united and built a city at Kiev, which became their capital. "Rus" means "the men who row" in Old Norse, as their origins were in Scandinavia, and the Vikings settled colonies that became the present-day countries of Russia, Belarus, and Ukraine. The Chuds, Slavs, Merians, and Krivichs ousted the Varangians and governed themselves, conquering the Rus Khaganate and founding their own kingdom.

Military history
The Rus tribespeople attacked Constantinople, capital of the Byzantine Empire, in both 860 and 907, and raided into The Balkans. Soon, Byzantine influence replaced their Paganism with Orthodoxy, a form of Christianity, and the Rus converted to this new religion, which is still strong in Ruthenia today. The Kievans had a rich state until the decline of Constantinople's trade, and they fell apart into the city-states of the Duchy of Novgorod, Duchy of Ryazan, Duchy of Moscow, Duchy of Smolensk, Duchy of Oka, Duchy of Kiev, Duchy of Vladimir, and the Volga Bulgars, and fought each other. By 1080, the court of Kiev's chaos ended any chance of peaceful unification, so the Novgoroders, led by Ysevolod I of Novgorod, took over every state, founding a Russian kingdom.